Yazsoft is out of the business. Please try the best alternatives for their solutions for free:

Folx is a powerful download manager and torrent client for Mac OS X that gives you ultimate capabilities when it comes to resuming interrupted downloads, splitting your downloads into multiple threads, regulation of the download speed and much more!
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What happened?

Since March 2014 Yazsoft has ended its business and stopped supporting its products.
All users of their most popular app Speed Download are recommended to try its powerful alternative - Folx.
Folx is a handy download manager and torrent client for Mac. It splits downloads in several threads, resumes interrupted downloads, controls download speed, offers efficient management system for downloaded files and much more!